Adhesive sheet product and method of making



Dec. 31, 1957 M. A. B'ERGSTEDT ET AL 2,818,349

ADHESIVE SHEET PRODUCT AND METHOD OF MAKING Filed Aug. 17, 1954` NORMALLY THCKY AND PRESSURE SENSITIVE AD/'lE/VE VV l /A af-J 4 CELLULOSE ACETATE BACK/NG MIRROR COAT/NG NK IMPRESSIONS INVENTORS,

M/LToN ALFRED BE/Pcsrfm; EURL WARD /lL-'y Je.

Mevr-744.... WW1, gun-Aw ATTORNEY United States Patent O ADHESIVE SHEET PRODUCT AND `METHD F MAKING Milton Alfred Bergstedt, Linden, and Burl Ward Keys, Jr., Highland Park, N. J., assignors to Permacel-Le Pages Inc., a corporation of New Jersey Application August 17, 19.54, Serial No.. 450,547 7 Claims. (Cl. 117-14) This invention relates to printed adhesive tape and to adhesivel tapes suitable for printing and processesv of making adhesive tape suitable for printing and of printing adhesive tape. The. invention is concerned particularly with normally tacky and pressurersensitive non-fibrous film-,backed adhesive tapes, the best known of which have.

adhesives of the rubber-resin type, out which may also be composed of polymers incorporating both robbery and resinous properties within the polymer. ln preferred aspects it is concerned with normally tacky and pressure-sensitive adhesive tape that is wound up in a roll with contact between adhesive coated and the adhesivefree sides of adjacent convolutions in the roll, and that is unwound thereafter before use.

Film-backed normally tacky and pressure-sensitive adhesive tapes have always been difficult to print. When the usual film-backed tape isA printed, the print offsets when the tape is rolled and unrolled, particularly if the printed tape is retained in roll form for prolonged periods of time or at elevated temperatures. In many cases printing increases adhesion to backing to such an extent that the ilm tape breaks and tears during unrolling or use. Theoretically it may be possible to anchor the print by applying double coats, one before and oneV after printing', or by isolating the printing between two films, laminated so as to prevent contact between the adhesive and the printing layer. Constructions of these types, however, are costly and result in bulky, unduly thick tapes that are unsightly and inconvenient to use, if not inoperative. In addition, in such constructions the print-` ingitends to run, so that a poorly defined impression results after overcoating and lamination.

It is an object of the invention to provide products and processes resulting in an ink impression anchored so tightly that no overcoating is necessary. A further object of the invention is provision of normally tacky and pres.-V sure-sensitive printed lm tape wherein ink lifting and ink transfer are prevented even when the ink impression isl in direct contact with strong adhesive. A still further object is provision of ink impressions on tape that are adapted to withstand a wide variety of conditions. Yet a further object is provision of an economical prOGQSs for efficient pressuresensitive film tape printing and of economical, eicient lm tape for printing and printed lilm tape. Still further objects of the invention will be readily apparent from the following description 0f the invention, which shows several preferred forms D. the invention furnished by way of example only and no t to limit the scope of the invention.

The drawing shows diagrammatically the printed adhesive tape prepared in accordance with the invention. In the drawing, 1 is the cellulose acetate backing, 2 is the normally tacky and pressure-sensitive adhesive, 3 is the mirror coating, and 4 is the ink impression.

In accordance with the invention, printed nlm tape is made by coating the film on one side with the adhesive coating or combination of coatings, which may include a primer for the adhesive, for instance as shown in Beim meis Patent No. 2,647,843, issued August 4, 1953, and

mirror coated on the other side with a patternless, ysubstantially waxand plasticizer-free tine polymeric coating, This mirror coating involves applying on `the lilm side opposed to the adhesive avery thin coating, using pattern-free solvent combinations. The mirror-coated lm may then be printed directly on the mirror coating, preferably using inks having a resinous binder, sometimes valso called iiexigraphic inks.

The preferred backing film ofthe invention is `a meis.- ture-sensitive film, usually plasticized. ,Said .films .are the ones most diicult toprint Successfully and permanently in absence of the invention, Particularly when the finished printed product encounters conditions of relatively high humidity. For many purposes cellulose acetate is preferred, although the invention may be vapplied to other highly moisture-sensitive, exible, high tensile films. Backings involving combinations of lms with strands, fibers, ber webs, e. g. paper or non-woven fabric, or other ilms may be substituted for plain lms, .provided that the smooth film withthe mirror vcoating appears `on the side available to accept the printing impression. The preferred film isr vcellulose acetate film of a thickness of from about one-half to about two and one-,half mils, plasticized with from about tive, to about forty percent of iS weight of plasticizer, usually of the liquid ester type, e. g .di-butyl phthalate.

The. preferred mirror coating is applied by knife coats ing, finely etched roll, vkiss coating or release or reverse roll coating to. a coating weight preferably not more than one-.quarter or one ounce per square yard, .and for goed results not more. than half of one ounce per .Square Yard, and comprises a material in its substantially unplasticized wax-free state having aflinity for the moisture-sensitive film, preferably the, lower alkyl methacrylate polymers, for best results ethyl methacrylate polymer, or nitrocellulose. Among the lower methacrylates that may also be used are methyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate and octyl rnethacrylate. The `lowest methaorv-lates are vgenerally more brittle than the higher ones, and therefore mirror coatings using ethyl or methyl rnethacrylate should be applied to lower coating weights than mirror-,coatings of, say, heptyl and Octyl methacrylate.

The mirror coatings may be ,applied from mixed solvents, and part of the mixed solvent should for best results be a true solvent for cellulose acetate, permitting the mirror coating solution to bite into the sheet. Within the above-stated ycoating weight limits the mirror coating thckness that is preferred depends upon the inherent flexibility or brittleness of .the Vcoating materials, while a, continuous, Coating as thin as possible without pattern formation` .is genrally most desirable.

The printing ink .used may be any ink having a resinous binder, sometimes .called flexigraphic ink. Among pre,- terred inks are inks based on binders such as shellac, `ethyl cellulose ,and nitrocellulose. Among preferred solvents for the luk are the lower aliphatic. alcohols and the lower aliphatie esters., e. s.. .ethyl acetate- The amount and. type et solvent is ,regulated .so as to give the ink the desired drying sneed and degree of penetration.

Typical inks are:

INK A Parts by weight Victoria blue R 2'75 (Color Index 728) l.-` d'2O Ethyl cellulose 5 Dissolved in methylated spirit INK EXAMPLE B Diacetone alcohol 20() National Vnigrosine base N 2() Orange shellac f 8l) 3 INK EXAMPLE c Parts by weight And mix thoroughly.

Examples of preferred forms of the invention follow:

Example I A two-mil cellulose acetate lm known as P-912 was coated with a primer composed of butadiene-acrylonitrile copolymer mixed with butadiene-styrene copolymer in accordance with Bemmels Patent 2,647,843, patented August 4, 1953, to form a primer coat weighing, dry, twotenths of one ounce per square yard. The ilm was then mirror coated on the side opposed to the primer with a patternless coating of one-tenth of one ounce dry weight of waxless, substantially unplasticized ethyl methacrylate applied from a ten percent by weight solution in one part ofvethyl acetate per tive parts of toluene. After drying of primer and mirror coating, the primed side was supercoated to a coating Weight of one ounce per square yard with a normally tacky and pressure-sensitive adhesive mass of the following formulation:

Parts by weight Crude natural rubber, pale crepe, well broken down 39 Rosin, dehydrogenated Filler such as zinc oxide and aluminum hydrate 30 Antioxidant 1 Very good results were obtained on printing this adhesive tape on the mirror coating, using resin bonded inks and any conventional printing process. Amounts of ink sufficient to give very good legibility and solid, dark impressions did not transfer, even after prolonged storage of the tape and under conditions of relatively high humidity.

' Example II Adhesive tape was made substantially in the manner of Example l except that the mirror coating was applied by a knife coater and comprised one-half second nitrocellulose, applied without creating a pattern on the cellulose acetate side of a combined backing composed of .00088 inch cellulose acetate lm laminated by rubberresin pressure-sensitive adhesive to two-mil manila rope paper. The coating was applied in absence of wax, to a dry coating weight of two-tenths of an ounce per square yard, using a solvent composition comprising equal parts by weight of butyl alcohol and ethyl acetate. The following normally tacky and pressure-sensitive adhesive was applied after mirror coating in a tandem operation:

Parts by weight A 75% butadiene, 25% styrene copolymer, well i Very good, durable printing resulted in this case.

4 Example III A two-mil cellulose acetate lm plasticized to the extent of twenty percent with a plasticizer of the di-methoxyethyl phthalate type, orother plasticizer with high boiling point and extremely low volatility, was used. To this lm were applied in one coating and drying operation a butadiene-acrylonitrile-copolymer-bntadiene-styrene-copolymer primer in accordance with the aforementioned Bemmels patent, and also a patternless mirror coating comprising a waxless, substantially unplasticized onesecond nitrocellulose solution consisting of forty parts by Weight butyl alcohol, forty parts ethyl acetate and twenty parts toluene. The primer and the mirror coating were applied to opposite sides of the lm, the primer to a coating weight of two-tenths of an ounce per square yard and the mirror coating to a coating weight of .001 of an ounce per square yard. Using nitrocellulose bonded flexigraphic ink, very satisfactory, secure, permanent impressions resulted on the mirror coating.

Either before or after printing, an adhesive was applied to lthe primed side of the backing, to a coating weight of one and one-half ounces per square yard, comprising the following formula:

Parts by weight Crude natural rubber, well broken down on the rubber mill 60 Oil-modified phenolic resin 2 Hydrogenated rosin glyceride 35 Alkylated polyhydroxy phenol 0.6 Lecithin 2 Example 1V This product was prepared in every respect the same as Example 1, except that the backing and initial or primer coat were prepared as follows: One and one-half mil commercial grade cellulose acetate lm was coated with a bonding coat composed of ten parts by weight of butadiene acrylonitrile polymer having a Mooney viscosity of fifty, and ten parts by weight of GR-S X245 butadiene styrene copolymer. The first copolymer was composed of seventy-live percent by Weight butadiene and twenty-five percent acrylonitrile. The second copolymer was composed of fty parts by Weight of butadiene and fifty parts by weight of styrene and had a Mooney viscosity of approximately 40-50. The bonding coat was applied from twenty percent by weight toluene solution to a coating weight of one ounce per square yard. To this bonding coat were applied forty strands per inch of fifty-tive denier cellulose acetate, fifteen filaments per strand, having a twist of ve turns per inch. To this coated combined backing was applied a normally tacky and pressure-sensitive adhesive composition comprising the following parts by Weight:

Parts by weight Smoked sheet natural rubber l() Zinc oxide 8 Hydrogenated cournarone-indene resin, melting point 70 C 8 Lanolin 3 Alkylated polyhydroxy phenol as age resistor 0.3 Toluene 70.7

The mirror coating employed was ethyl metacrylate polymer applied from a solution comprising forty parts by weight of ethyl methacrylate polymer in sixty parts by weight ethyl acetate and three hundred parts by weight of toluene. The mirror coating was applied using an etched print roll. Using a knife coating, a solution of forty parts by Weight ethyl methacrylate polymer in sixty parts by Weight of ethyl acetate is preferred.

Example V This example was prepared in every respect the same as Example II, except that the one-half second nitrocellulose was slightly plasticized, using three per cent by Weight di-octyl phthalate.

The invention has been described in its preferred form, and many modifications thereof are included within its spirit.

We claim:

1. A normally tacky and pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive united to one surface of a flexible, non-fibrous, cellulose acetate backing iilm, and, united to the other surface of said backing, a continuous mirror coating comprising at least a major proportion of at least one member of the group consisting of the lower alkyl methacrylates and nitrocellulose, and, applied directly to said continuous mirror coating, resinous binder ink impressions, said sheet being in package form wherein the printed side of said mirror coating directly contacts said adhesive.

2. In the process of preparing printed cellulose acetate film-backed normally tacky and pressure-sensitive adhesive tape, the steps of preparing the adhesive tape backing for a resinous binder ink impression by pre-coating the ink receiving surface of said backing with a thin, continuous, mirror coating comprising at least a major proportion of at least one member selected from the group consisting of the lower alkyl methacrylates and nitrocellulose, and applying resinous binder ink impressions on said mirror coating.

3. The process of claim 2 wherein said mirror coating comprises a lower methacrylate polymer.

4. A process in accordance with claim 2 wherein said mirror coating comprises ethyl methacrylate polymer.

5. A product in accordance with claim 1 wherein said mirror coating comprises a lower alkyl methacrylate polymer.

6. A product in accordance with claim 1 wherein said mirror coating comprises ethyl methacrylate polymer.

7. A product in accordance with `claim 1 wherein said mirror coating is composed of nitrocellulose.

References Cited in the le of this patent UNITED STATES PATENTS 2,269,712 Drew Ian. 13, 1942 2,438,195 Tierney Mar. 23, 1948 2,599,576 Morris June 10, 1952 2,607,711 Hindricks Aug. 19, 1952 2,656,286 Fisher Oct. 20', 1953 

2. IN THE PROCESS OF PREPARING PRINTED CELLULOSE ACETATE FILM-BACKED NORMALLY TACKY AND PRESSURE-SENSITIVE ADHESIVE TAPE, THE STEPS OF PREPARING THE ADHESIVE TAPE BACKING FOR A RESINOUS BINDER INK IMPRESSION BY PRE-COATING THE INK RECEIVING SURFACE OF SAID BACKING WITH A THIN, CONTINUOUS, MIRROR COATING COMPRISING AT LEAST A MAJOR PROPORTION OF AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF THE LOWER ALKYL METHACRYLATES AND NITROCELLULOSE, AND APPLYING RESINOUS BINDER INK IMPRESSIONS ON SAID MIRROR COATING. 